Modification assembly for changing semiautomatic firearms selectively into fully automatic firearms

ABSTRACT

A modification assembly for a semiautomatic firearm includes a sear disconnector, a hammer catch and a fire control selector that cooperate in enabling the weapon to be selectively fired in either a fully automatic or semiautomatic mode of operation. The sear disconnector prevents the sear piece from catching the hammer during counterrecoil of the bolt if the trigger piece is fully depressed and is carried by and movable with the trigger. The hammer catch is spring biased to a position at which it interrupts forward movement of the hammer during the fully automatic mode of operation and is so arranged in the modified firearm as to be actuated to release the hammer by the movement of the firing pin as the bolt closes during its counterrecoil. The fire control selector is manipulatable to permit the weapon user to select the desired mode of operation and has a bolt catch which during the semiautomatic mode of operation is spring biased to a position at which it catches the bolt during its counterrecoil and thus interrupts its movement into its locked position. Release of the bolt is accomplished during the semiautomatic mode of operation by a separate manipulation of the selector by the weapon user.

Elnfited States Patent Inventor Lewis D. Shiplee, III

818 Concord Road, Tallahassee, Fla. 32303 Appl. No. 866,898 Filed Oct. 16, 1969 Patented Dec. 14, 1971 MODIFICATION ASSEMBLY FOR CHANGING SEMIAUTOMATIC FIREARMS SELECTIVELY INTO FULLY AUTOMATIC FIREARMS 9 Claims, 22 Drawing Figs.

Primary Examiner- Benjamin A. Borchelt Assistant Examiner-Stephen C. Bentley Attorney-Roger l... Martin ABSTRACT: A modification assembly for a semiautomatic firearm includes a sear disconnector, a hammer catch and a fire control selector that cooperate in enabling the weapon to be selectively fired in either a fully automatic or semiautomatic mode of operation. The scar disconnector prevents the sear piece from catching the hammer during counterrecoil of the bolt if the trigger piece is fully depressed and is carried by and movable with the trigger. The hammer catch is spring biased to a position at which it interrupts forward movement of the hammer during the fully automatic mode of operation and is so arranged in the modified firearm as to be actuated to release the hammer by the movement of the firing pin as the bolt closes during its counterrecoil. The fire control selector is manipulatable to permit the weapon user to select the desired mode of operation and has a bolt catch which during the semiautomatic mode of operation is spring biased to a position at which it catches the bolt during its counterrecoil and thus interrupts its movement into its locked position. Release of the bolt is accomplished during the semiautomatic mode of operation by a separate manipulation of the selector by the weapon user.

Patented Dec. 14, 1971 3,626,8fl5

4 Sheets-Sheet l LEWIS .0. SHIPLEE III INVIfN'IOR.

Patented Dec. 14, 1971 3,626,85

4 Sheets-Sheet 2 \FIG. 5

/4 F IG. 6 a

LEWIS D. SHIPLEE m INVENTOR.

Patented Dec. 14, 1971 4 Sheets-Sheet 5 LEWIS D. SHEPLEE m wme Patented Dec. 14, 1971 4 Sheets-Sheet 4 FIG. I8

LEWIS D. SHIPLEE INVENTOR.

MODIFICATION ASSEMBLY FOR CHANGING SEMIAUTOMATIC FIREARMS SELECTIVELY INTO FULLY AUTOMATIC The present invention relates to semiautomatic weapons and more particularly to improved modifying assemblies therefor and which permit the weapons to be fired in a fully automatic mode of operation.

The various aspects of the invention can be singularly or collectively used in the modification of various different types of semiautomatic weapons but are most particularly described hereinafter as embodied in the modification assembly for the U.S. M1 30 caliber carbine.

In the past an extremely large number of U.S. Ml carbines have been manufactured and consequently, there is a large surplus that has been stockpiled by the government. Due to the large surplus of this weapon, there are have been several attempts to modify the weapon so that it will fire in a fully automatic mode and thereby increase its fire power and make it is effective as modern day fully automatic weapons. ln general, the proposed prior art modification assemblies have been structurally too complicated to provide an effective and efircient weapon for use in the field by foot soldiers. Structurally, the modifying assemblies are too complicated and substantially reduce the operational reliability of the weapon as well as make the weapon difficult and time consuming to assembly during field usage. Practically all of the prior art attempts to modify the weapon have required the remachining of various parts of the weapon and this, of course, it is not only expensive but renders it impossible to modify the weapons that are in actual field use without the need for recalling the weapons to efiectuate the modifications. Other objections to the prior art attempts at modifying such weapons reside in the lack of safety features that are adequate to prevent the misfiring of the weapon during its fully automatic usage.

The embodiment of the invention described hereinafter can be easily incorporated in the semiautomatic weapon without the need for the expensive and time-consuming remachining or reworking of the existing weapon parts as is characteristic for the prior art modifying devices previously proposed. Furthermore, the modification assembly advocated herein embodies such simple structural features that the parts can be rapidly installed in the field by the average soldier with a minimum amount of training or instruction.

A general object of the invention is to provide improved devices for modifying semiautomatic weapons and which enable the weapons to be fire in a fully automatic mode of opera- IlOIl.

Another object of the invention is to provide means for modifying semiautomatic weapons so that they are capable of fully automatic usage without the need for replacing parts of the weapon or of remachining such parts so as to accomplish the desired modifications.

Yet another object of the invention is to provide inexpensive means for modifying U.S. M1 30 caliber carbines to facilitate their fully automatic usage and which can be in stalled in the field by the average foot soldier without appreciable instructions.

Another object of the invention is to provide a modification assembly for M1 30 caliber carbines that permits their usage as fully automatic weapons and which provides good operation reliability in actual usage.

Yet another object of the invention is to provide improved operational safety features in such modification assemblies and to provide simple and inexpensive assemblies for converting the carbines to fully automatic weapons.

When semiautomatic weapons of the M1 30 caliber carbine type are cocked, the nose of the sear piece engages the hammer in a recess to hold it in its cocked position. To release the hammer so that it moves under the urgings of the hammer spring to its firing position, the trigger piece is caused to pivot about the trigger pin to its fully depressed position. The trigger piece has a lip which normally underlies the tail of the sear piece when the hammer is cocked and the trigger piece is in its undepressed or normal bias position. As the lip rises and encounters the tail during depression of the trigger, the sear is caused to pivot about the axis of the trigger pin and ultimately to a position at which the nose of the sear piece is drawn downwardly and dislodged from the hammer recess. This, of course, releases the hammer to fire any round that may be in the firing chamber.

Weapons of this type automatically discharge the empty shell casing and reload the firing chamber with another round. The action is such that as soon as the round as been fired, the bolt automatically recoils to permit the discharge of the shell casing from the weapon. As the bolt recoils and opens the firing chamber it encounters and pivots the hammer backwardly beyond its cocked position. Following this, there is an automatic counterrecoil of the bolt so that the next round to be fired is shoved into the firing chamber of the weapon by the counterrecoiling bolt action. During this counterrecoil of the bolt, the hammer, having overrode its cocked position during recoil, pivots forwardly toward its firing position and is again caught at its cocked position by the sear piece.

Those familiar with M1 30 caliber carbine-type weapons realize that the recoil and counterrecoil of the bolt transpires so rapidly that the weapon user rarely, if ever, has a chance to release the trigger piece before the next round has been chambered. As a result, the trigger and sear pieces are so mounted and constructed that the sear moves into a position at which its nose engages the hammer in its recess during counterrecoil of the bolt even through the trigger piece is fully depressed. To accomplish this, the sear piece is not only mounted for pivotal movement on the trigger pin of the weapon but is provided with a slot in which the trigger pin engages the sear piece. The slotted arrangement permits the sear piece to be shoved forward on the pin toward the hammer under the urgings of the sear spring as soon as the sear nose is dislodged from the hammer recess. This movement draws the tail of the sear forward of the trigger lip and over another recess that is located in front of the lip of the depressed trigger piece. The scar spring is also arranged to pivotally bias the sear piece about the axis of the trigger pin and in a direction that causes the nose to encounter a cam surface of the hammer as the hammer moves to its firing position. This cam surface merges with the recess or notch defining surface of the hammer, so that during the recoil of the bolt, the sear spring pivotally urges the sear nose into the notch as the hammer overrides the cocked position. As this happens, the sear tail pivots downwardly into the recess of the trigger piece if the trigger piece remains depressed, and thereafter as the hammer returns to the cocked position during the counterrecoil of the bolt, it is caught by the nose of the sear. As the hammer is caught by the nose, it shoves the sear back on the firing pin and to a position at which the tail encounters a lip side portion of the depressed trigger. As such, even though the trigger piece is fully depressed, the hammer is caught in its cocked position during the counterrecoil of the bolt action. As the hammer is thus caught, the need arises before the next round can be fired, for the weapon user to release the trigger pressure so as to permit the trigger lip to pivot under the biasing force of the trigger spring downwardly to a position below the sear tail. As this happens, the hammer moves slightly forwardly in its cocked position and the sear piece is s shoved back further on the trigger pin by the hammer assembly and to a position at which the sear tail again overlies the trigger lip.

One aspect of the invention has to do with a sear disconnector which is carried by and mounted on the trigger piece. The sear disconnector is adapted to be held in place on the trigger piece by the trigger spring and has a portion that overhangs the trigger recess. The overhang provides a forward extension for the lip and prevents the sear tail from moving into the trigger recess as the hammer overrides its cocked position. As such, it also prevents the sear nose from entering the hammer recess to catch the hammer during the counterrecoil of the bolt. The one piece structure of the sear disconnector makes it simple to manufacture and the means used for mounting the disconnector avoids unnecessary parts. Use of the disconnector, of course, limits movement of the sear piece, and while the trigger piece is depressed it serves as a means for disconnecting the sear from the hammer action.

Another aspect of the invention relates to a catch for the hammer and which, in assemblies designed for the modification of such semiautomatic weapons to render them fully automatic, temporarily interrupt forward movement of the hammer during the counterrecoil of the bolt so as to assure closure of the bolt before the hammer strikes the firing pin. The hammer catch is mounted for limited pivotal movement between the stock of the gun and an external sidewall of the trigger housing, and is spring biased to a position at which a detent forming portion is encountered by a lug on the hammer during the latters forward movement. The catch is actuated to release the hammer by a rotational or pivotal movement of the firing pin as the bolt closes during its counterrecoil action. Although the principle involved in actuation the catch can be embodied in devices mounted in manners other than that shown hereinafter, one feature involved in this aspect of the invention resides in securing the catch in place by means of the hammer pin so as to avoid machining of parts and other attachment devices.

A third aspect of the invention has to do with a fire control selector assembly which allows the user of the firearm to operate it in either an automatic or semiautomatic mode of operation. The selector is mounted at the exterior of the weapon and has a spring biased lug or bolt catch which through manipulation of a connected lever can be positioned to catch the bolt during its counterrecoil when a semiautomatic mode of operation is selected. In lieu of this, it can be pivoted to an inoperative position for the full automatic mode of operation of the weapon. In principle the selector serves to catch the bolt rather than the hammer in the semiautomatic mode of operation, and this requires manipulation of the connected lever to release the bolt as well as manipulation of the trigger finger in order to fire the next round in this mode of operation.

The novel features which are believed to be characteristic of this invention are set forth with particularity in the appended claims. The invention, itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings, in which:

FIG. la through FIG. le inclusive are a series of diagrammatic illustrations showing the internal structural elements of the trigger housing of a US. M1 30 caliber carbine in various positions they assume during the normal semiautomatic firing sequence when the weapon is unmodified by the modifying assembly advocated herein;

FIG. 2 is an enlarged perspective view of a sear disconnector used in a weapon-modifying assembly embodying the various aspects of the invention;

FIGS. 3 and 4 are outside and inside perspective views of the hammer catch assembly of the subject modification assembly;

FIG. 5 is a side elevational view of the trigger housing assembly and adjacent structure of an MI 30 caliber carbine as seen when the sear disconnector and the hammer catch are mounted in the weapon with certain parts being broken away and others removed;

FIG. 6 is a fragmentary sectional view taken along the lines 66 of FIG. 5;

FIG. 7 is a fragmentary side elevational view that shows the position of the catch and sear piece during full automatic operation of the weapon and at the time the hammer is interrupted in its forward movement by the catch;

FIG. 8 is a sectional view taken along the lines 8-8 of FIG.

FIG. 9 is a sectional view taken along the lines 9-9 of FIG. 7, with certain parts removed and others broken away;

FIG. 10 is a side elevational view showing the relationship of the hammer catch and sear disconnector to the sear, hammer and trigger assemblies, as the hammer strikes a firing pin;

FIG. 11 is a fragmentary sectional view taken along the lines llllll of FIG. M), with certain parts removed and others broken away;

FIG. 12 is a perspective view of a fragment of an Ml carbine as seen with the fire control selector mechanism mounted thereon, certain parts being broken away;

FIG. 13 is an enlarged top plan view of the fire control selector as seen in FIG. 12 with certain parts broken away;

FIG. 14 is a side elevational view of the fire control selector mechanism with parts broken away;

FIG. 15 is a sectional view taken along lines 15-15 of FIG. 14 with parts of the receiver and bolt shown in broken lines;

FIG. 16 is an enlarged perspective view of a fragment of the fire control selector mechanism;

FIG. 17 is a view taken along the lines 17-17 of FIG. 12 with certain parts removed; and

FIG. 18 is a sectional view taken along the lines 18-18 of FIG. 14.

The structure of the various parts of a US. MI 30 caliber carbine and how they fit together in the assembled weapon are well known but to more clearly understand the specific operation of the weapon as modified by the illustrated embodiment of the invention, reference is first made to FIGS. la through 1e inclusive for a description of the operating sequence of the hammer, sear and trigger assemblies in the unmodified weapon.

The semiautomatic weapon includes a trigger assembly, generally indicated at 10, a sear assembly, generally indicated at 12, and a hammer assembly, generally indicated at 14.

The trigger assembly 10 comprises a trigger piece 11 which is mounted for limited pivotal movement on the trigger pin 28 and also comprises a trigger spring 18 which biases the piece 1 I toward its normal or released position 15 as in the direction of arrow 17 (see FIG. la). The trigger piece 11 has an upright lip portion 20 that normally underlies the tail 24 of the sear piece 13 and also has a groove containing ledge 19 behind the lip which is engaged by the spring in the assembled weapon. In front of the lip, the piece 11 has a recess 22 which is provided to accommodate certain movements of the sear tail 24, as will appear subsequently.

The scar assembly 12 includes the sear piece 13 and a compression spring 32. The trigger pin 28 extends through a pair of transversely spaced lugs 21 of the trigger piece, and the body portion 23 of the sear l3 fits between the lugs 21. The body portion 23 has an elongated slot 30 through which the pin 28 extends and which permits pivotal movement of the sear about the axis of the trigger pin and also permits limited sear piece movement transverse to the axis. The tail 24 of piece 13 extends rearwardly of the body portion 23 to cooperate with the trigger assembly while the nose 26 of the sear piece extends forward in the assembled weapon to cooperate with the hammer assembly I4. The trigger piece 11 has a bore 29 that opens into the space between the lugs 21 and the sear spring 32 fits in the bore 29 with one end engaging the sear piece 13 in a suitable bore 31 therefore.

The hammer assembly 14 includes the hammer 34 and a pin component 36 on which the hammer is mounted for limited pivotal movement. The head of the plunger component 40 of assembly 14 fits in a suitable recess 40a (FIG. 6) in the hammer, and the compression spring component 38 of the hammer assembly 14 is coiled about the plunger 40 where it serves to bias the hammer 34 to pivot forwardly in the direction of arrow 25.

FIG. Ia shows the trigger piece in its released position 15 and the hammer 34 in its cocked position 27. As such, the weapon is ready to be fired and the nose portion 26 of the sear piece 13 is engaged in a latching recess or notch 42 at the base of the hammer. Under such circumstances, the biasing force exerted on the hammer 34 by the hammer spring 38 is such as to urge the sear piece 13 backwardly on the trigger pin 28 against the reactive force of the sear spring 32 so that the tail 24 of the sear piece 13 overlies the trigger lip.

FIG. llb shows the trigger piece 11 in a partially depressed position 33 and after it has been pivoted in the direction of arrow 35 against the biasing force of spring 18 to bring the lip 20 into underside contact with the sear tail 24. Further depression of the trigger piece 11, under such circumstances, will cause the sear piece 13 to pivot about the axis of pin 28 and hence dislodge the sear nose 26 from the hammer recess 42 to permit the hammer 34 to pivotally move into its firing position.

FIG. 1c shows the trigger assembly in a fully depressed position 37 and the hammer in its firing position. The nose 26 of the sear piece 13, under such circumstances, has been dislodged from the hammer recess 42 by pivotal movement of the sear piece 13 in the direction of arrow 35 under the influence of the trigger piece 11. As the nose 26 disengages the hammer 34, the sear spring 32 forces the sear piece 13 forwardly on the trigger pin 28 in the direction of arrow 41 while continuing to pivotally urge the sear piece 13 in the direction of arrow 43. This causes the nose 26 to ride the cam surface 44 of the hammer 34 during the firing stroke and thereafter until the hammer returns and overrides its cocked position during the recoil of the bolt. The sear piece 13 movement in the direction of arrow 41 that is permitted by reasons of the slotted arrangement is such as to draw the sear tail forwardly of the trigger lip 20 and over the recess 22 in front of the lip, as seen in the figure.

FIG. 1d shows the trigger piece 11 in its fully depressed position 37 while the hammer 34 is shown in the override position 45 it assumes at the completion of the bolt recoil and the commencement of its counterrecoil action. During recoil of the bolt, the hammer 34 has been caused to pivot in the direction of arrow 47 beyond its cocked position. As it passes the cocked position 27, the sear spring 32 urges the sear nose 26 into the hammer recess area 42 and also urges the tail end into the trigger recess 22 by pivotally moving the piece 13 in the direction of arrow 49. The nose 26 is accordingly in a position to catch the hammer 34 as the bolt returns to the locked position during its counter recoil action.

FIG. 1e shows the next step in the operating sequence. Here the trigger piece 11 is still in its fully depressed position 37 and the hammer 34 has started to pivot in the direction of arrow 25 and back to its cocked position as the bolt counterrecoils. As the hammer moves in this direction 25, the sear nose 26 becomes fully seated in the hammer recess 42, and the hammer action is such as to shove the sear piece 13 backwardly in the direction of arrow 51 to a position at which the tail 24 engages the front side 53 of the lip. This retains the hammer in an interum position 55 until the trigger piece is released.

Upon release of the trigger pressure, spring 18 automatically pivots the trigger piece 1 l in the direction of arrow 17 to its released position 15. As this happens, the lip rides down the tail extremity into a lower position with respect to this portion 24 of the sear piece 13, and the hammer pivots to its cocked position 27 by a slight forward movement that forces the sear further back on pin 28 and to a position at which the tail overlays the lip. Thereafter the operating sequence can be repeated.

The scar disconnector component of the modifying assembly is generally indicated at 46 in FIG. 2. The sear disconnector 46 is made of a single piece of metal or other suitable material and is so adapted or shaped as to fit onto the trigger lip 20 and be held in place by the trigger spring 18 (see FIGS. 5 and 7). In this respect, the disconnector 46 has an end portion 48 which is bent to fit into the groove 57 of the trigger ledge 19 and here the selector provides an auxiliary groove 50 in which the trigger spring 18 is received. The remaining portion of the sear disconnector includes a middle portion 52 that overlies the lip 20 and a front end portion 54 which overhangs the recess area 22 in front of the lip, as is seen in FIGS. 5 and 7. This front portion 54 is arranged in a slight angular relationship to the middle portion 52 to facilitate sliding movement of the sear tail on the disconnector during the full automatic mode of operation of the weapon.

The sear disconnector 46 can be used alone to convert the semiautomatic weapon to full automatic usage, but to avoid the possibility of premature firing and as a safety feature, the use of a hammer catch device 56 is advocated. This catch device 56 is adapted for mounting between the interior wall of the stock 82 and the left sidewall 73a of the trigger housing, as seen in FIGS. 6 and 8. Device 56 includes a one piece metal element or component 59, a prefon'ned spring 66, and an elongated element 61 on which the spring is coiled and which is secured to the metal element 59 by a pair of spaced flapped portions 67 that are formed in the element 59. The metal element or component 59 is cut and bent as seen in FIGS. 3 and 4 and has a generally flat body portion 58 which is located at the exterior of the housing when the device 56 is mounted on the weapon. One end portion 63 of spring 66 is bent at an angle as seen in FIGS. 6 and 8 to bear against the stock wall 80, and the end extremity 65 projects through a hole 69 in the body portion that is provided to accommodate movement of the element or component 59 relative to the spring end 63. The body 58 of element 59 has an aperture 68 to accommodate the location of the head 75 of the hammer pin 36. The device 56 rests on the housing ledge 77 below the pinhead 75 and the aperture 82 is somewhat larger than the head 75 so that the metal element 59 can more or less pivotally move between its operative or hammer interrupting position 79, shown in FIG. 8, and its disengaged position 81, seen in FIG. 6.

The hammer 34 has a lug 72 which, at its firing position 39, engages the housing wall 73a at the hammer stop forming upper edge 83 that defines the left side opening 85 into the interior of the housing. The metal element 59 of the catch device 56 has a portion 60 that is bent inwardly from the body portion 58 to provide a detent that is engaged by the hammer lug 72 during the firing stroke of the hammer 34 so as to interrupt the hammer movement. This detent is generally arranged above edge 83 when the element 59 is in the interrupted or operating position 79 for the component 59 and moves to the exterior of the housing when the metal component 59 is moved to the disengaged position 81 as will be seen subsequently.

In addition to the detent forming portion 60, the element 59 has a wing portion 62 which is bent more or less at right angles to the body portion 58 so that it projects inwardly through the opening 85 and in front of the position the hammer assumes at its firing position 39. This wing portion 62 generally underlies the bolt 78 and the end 63a of the wing is arranged to encounter the right sidewall 71 of the housing when the metal component 59 of the catch device 56 assumes its interruptive position 79. The metal component is loosely held in place by the head of the hammer pin 36 and this wall encountering arrangement of the wing 62 tends to minimize movement at the bottom of the body portion 58 which is caused for reason for the loose connection and which occurs when the component is urged into its operating position 79 from its inoperative position 81 by spring 66.

The wing 62 has an upright extension which is suitably bent to provide a lug 64 that underlies the bolt 78 in the path of movement of the lug 87 of the firing pin 74 when the one piece component 59 is in its hammer interruptive position 79 as seen in FIGS. 5 and 8. As the bolt 78 rotates in the direction of arrow 89 to its locked position 91 at the conclusive of its counterrecoil, the firing pin lug 87 engages the lug 64 of component 59 and pivots the component 59 against the biasing force of spring 66 and into a disengaged position 81, as seen in FIG. 6.

The mode of operation and function of the sear disconnector and hammer catch device during full automatic usage of the weapon are best seen by reference to FIGS. 5 through 11 inclusive.

In FIG. 5 the hammer is seen in its normal cocked position 27 at which the hammer is held against the biasing force of spring 38 by the engagement in the hammer notch or recess 42 of the sear piece nose 26. Under these circumstances, the sear piece 13 has been shoved backwards on pin 28 by the forces tending to pivot the hammer 34 in the direction of arrow 25 so that the sear tail 24 overlies the lip 22 and also overlies the portions 52 and 54 of the sear disconnector.

As for the catch device 56, the metal component 59 of this device 56 is, under the circumstances shown in FIGS. and 6, held in its disengaged position 81 against the biasing force of the spring 66 by the firing pin lug 87. Lug 87, as seen in FIG. 6, has engaged the wing lug 64 during closure of the bolt 78 and has caused the metal component 59 of device 56 to pivotally move into its disengaged position 81 as the bolt 78 assumes its locked position 91 at the conclusion of its counterrecoil.

The trigger piece 11 of FIG. 5 is shown in its released or normal position 15 and as the trigger piece 11 is depressed and pivotally moved in the direction of arrow 35 to its fully depressed position 37 as seen in FIG. 10, the sear piece 13 is caused, as the sear disconnector 46 engages the sear tail 24, to pivot in the same direction.

When the sear nose 26 is dislodged from the notch or recess 42 by the trigger movement, the hammer 34, of course, pivots about pin 36 under the urgings of the hammer spring 38 in the direction of arrow 25 and strikes the firing pin 74 to discharge any round in the shell chamber. As the sear nose 26 is dislodged from the recess 42, the sear spring 32 shoves the sear piece 13 forwardly on the trigger pin 28 in the direction of arrow 41 (FIG. and also tends to urge the piece 13 to pivotally move in the direction of arrow 43 (FIG. 10). This movement of the sear piece 13 draws the tail 24 forwardly on the disconnector 46 and to a position, as seen in FIG. 10, at which the tail 24 overlies the trigger recess 22 but is nevertheless prevented from pivoting into the recess 22 of the fully depressed trigger piece 13 by the overhanging portion 54 of disconnector 46. The seat tail 24 is accordingly supported on the overhanging portion 54 of the disconnector when the trigger piece 11 is in its fully depressed position 37, and under such circumstances, the nose 26 is incapable of entering the notch or recess 42 until the trigger pressure is released.

The metal component 59 of the catch device 56 remains in its disengaged position 81 as the hammer 34 moves from its cocked position 27 to its firing position 39. After discharge of the round in the firing chamber however, the bolt 78 starts to recoil and unlocks by pivotally moving in the direction of arrow 93 from its locked position, shown in FIG. 11 at 91, to its unlocked position, seen in FIG. 8 at 97. As this happens, the lug 87 of the firing pin 74 pivots away from the disengages lug 64 and the spring component 66 of the catch device 56 then urges the component 59 toward its hammer engaging position 79. This causes the bent detent forming portion 60 of component 59 to bear against the side of the hammer lug 72 as the hammer 34 is driven backwardly by the recoil action of the bolt 78.

As the hammer 34 overrides its normal cocked position 27 during recoil of the bolt 78, it pivots far enough in the direction of arrow 99 (FIG. 7) to clear the contact edge 101 of the detent forming portion 60. As this happens, the hammer lug 72 rides off the detent portion 60, and the spring component 66 forces the component 59 of device 56 into its operating or hammer interruptive position 79 at which the detect 60 is located in the path of forward movement of the hammer (FIG. 8). The lugs 64 of the rigid component under such circumstances is in the path of rotative movement of the firing pin lug 87 and hence engageable by the lug 87 when the bolt rotates into its locked position. Thereafter, as the bolt 78 starts its counterrecoil action, the hammer 34 moves pivotally :"orward in the direction of 25 (FIG. 7) and the hammer lug 72 engages the edge 101 of the detent portion 60. With this engagement, the hammer is temporarily held against the urgings )f the hammer spring 38 in the position 103, shown in FIG. 7.

Now during the full automatic mode of operation of the veapon, the trigger piece 11 remains in the depressed position l7 seen in FIG. 7 so that the sear nose 26 is incapable of enterng the notch or recess 42. Consequently, as the bolt 78 coninues its counterrecoiling action after the hammer 34 has been caught by the catch device 56, the hammer 34 remains in position 103. At the conclusion of the counterrecoil, the bolt 78 rotates in the direction of arrow 89 (FIG. 8) as the bolt closes and assumes its locked position 91. As this happens, the

firing pin lug 87 rotates or pivots into contact or engagement with the wing lug 64 of the metal component 59 and forces the component 59 into its disengaged position 81. This movement of component 59 against the urgings of spring 66 dislodges the detent 60 from the hammer lug 72 and disengages the edge 101 from lug 72. As a result, the hammer 34 continues its forward movement in the direction of arrow 25 and again strikes the firing pin 74 to discharge the next round fed into the chamber during the counterrecoil of the bolt. Thereafter, the operating process repeats itself with the catch device temporarily interrupting the forward movement of the hammer 34 until the bolt locks with each round successively fired and as long as the trigger remains in a fully depressed position.

To discontinue the full automatic sequence, the weapon user merely releases the finger pressure on trigger piece II. This permits the trigger piece 11 to pivot under the urgings of the trigger spring 18 into its released position 15. If the hammer 34 at the time the trigger is released, is in a position at which the sear nose 26 will pivot into the hammer recess 42 under the biasing force of spring 32, the hammer 34 will be caught by the sear nose and its forward movement stopped at its cocked position 27. As this happens, the sear piece 13 will be forced backwardly on the trigger pin 28 and to a position at which the sear tail again overlies the trigger piece lip 20 and middle body portion 52 of the disconnector. If the hammer 34 at the time the trigger is released is in a position at which the sear nose 26 will pivot into contact with the cam surface 44, the sear nose will be urged against the surface and thereafter into the recess of the hammer as the hammer subsequently overrides its cocked position in the normal operating sequence of the weapon. The hammer 34, of course, will then be temporarily interrupted in its forward movement as the bolt counterrecoils, but as soon as the bolt closes and the catch device is dislodged, the hammer 34 will be caught by the sear nose to stop the operating sequence.

From the foregoing description it is apparent that the sear disconnector 46 and the hammer catch device 56 can be used to convert the semiautomatic Ml carbine to a fully automatic weapon. As thus modified, the weapon can be fired in the semiautomatic mode of operation without removal of the modifying components by the use of the fire control selector 84 illustrated in FIG. 12.

The selector 84 of the modifying assembly is mounted on the exterior of the weapon as seen in FIG. 12 and includes a yoke 114 which is fixed to the rear end of an elongated tubular housing component 86 of the selector. The housing 86 is equipped at its rear end with a flangelike laterally projecting member 102 that is notched to cooperate with a spring biased bolt catch assembly that forms a component of the selector 84.

The yoke 114 generally conforms to the shape of the weapon at the base of the receiver and is secured to the weapon by the threaded type fastener 118 that secures the receiver catch to the stock of the weapon. The yoke 114 also has a lug 116 that engages the receiver in the slide groove at the right side of the weapon so as to hold the selector secured in place.

The bolt catch assembly 120 includes an elongated rod 88 which is housed in the tubular housing 86. The rear end of rod 88 is equipped with a lever component 84 of the assembly 120 while the front end of the rod is equipped with a lug 104 that projects laterally of the rod axis and forms a bolt-catching component of the assembly 120.

The rod 88 has a reduced end portion 107 of smaller diameter so as to accommodate a preformed spring component 108 of the selector and which is coiled about the rod 88 and located in the housing. One end 1 10 of the spring 108 fits in an elongated slot 112 that is provided in the end of the housing 86 to facilitate the assembly and disassembly of the bolt catch assembly parts whereas the other end 105 fits in a bore provided in the collar 113 or lug 104.

The front end extremity 109 of rod 88 is threaded, and the lug 104 is secured on the end 109 by a nut 111 that bears against the collar 113 while a setscrew 106 which is threaded in the collar 113 is used in rotatably orienting the lug on the rod to adjust its operative position.

As seen in FIG. 13, the lug 104 is normally offset from the front extremity of the housing 86. Rod 88 is arranged for limited axial and rotational movement in the housing 88 and the spring 108 is arranged to bias the catch assembly 120 axially forward in the direction of arrow 121 (FIG. 13) and also rotatably in the direction of arrow 123 (FIG. 15).

Lever 94 has a collar 90 which is fixed to the rear end of rod 88. This collar 90 normally bears against the rear end extremi ty of the housing 86 under the axial urgings of spring 108 in the direction of arrow 121. The lever 94 has a forward projecting side edge 96 which is offset from collar 90. The adjacent flange 102 has a pair of notches 98 and 100 which are adapted to receive the side edge 96 in accord with the mode of operation selected by the weapon user.

FIG. 15 shows the position 130 of lug 104 relative to the bolt 78 when the selector lever 94 is engaged in the lower notch 100 of flange 102. Under such circumstances, the lug or catch 104 is in an inoperative position, and the weapon can be fired in the fully automatic mode of operation previously described.

To place the catch assembly 120 in position for semiautomatic usage of the weapon, lever 94 is drawn rearwardly against the biasing force that is exerted in the direction of arrow 121 by spring 108. This manipulation of the lever 94 draws the catch assembly 120 rearwardly to the broken line position 132 seen in FIG. 13 and withdraws the lever edge 96 from notch 100. Thereafter, the lever 94 is manipulated to pivot the assembly 120 in the direction of arrow 134 (FIG. 18) and then released so that the spring 108 draws the lever edge 96 forwardly into the upper notch 98 of flange 102. If the bolt 78 is closed when the lever is manipulated into notch 98, the lug 104 will encounter the side 136 of the bolt 78 and will assume a position generally indicated at 138 in FIG. 15. Under such circumstances, the edge 96 of lever 94 will be only partially drawn into the notch 98 and will bear against the cam surface 99 shown in FIG. 16. Spring 108, as previously indicated, biases the assembly 120 in the direction of arrow 134. As such, when the breach is thereafter opened by drawing the bolt rearwardly of lug 104, either through manipulation of the slide or by the automatic recoil of the bolt when a shell is fired, the spring 108 will urge the lug 104 into the solid line position shown seen in FIG. 15. This, of course, positions the lug 104 in front of the bolt and stops subsequent forward movement of the bolt. As the lug 104 pivots and assumes the solid line position 140, the assembly 120 moves slightly forward in the housing under the urgings of spring 108 and the lever edge 96 rides down the cam surface 99 so that the lever becomes fully seated in notch 98.

When the bolt 78 is caught by the catch assembly 120, as seen in FIG. 12, the lever is fully seated in notch 98. To close the breach, the weapon user merely draws the lever downwardly sufficiently far enough to release the bolt. This occurs as the edge 96 rides up the cam surface 99 but before the edge becomes dislodged from the notch, so that by releasing the lever 94 as the bolt 78 is released by lug 104, the lever will remain in the notch 98 provided for the semiautomatic mode of operation so that the lug 104 will thereafter bear against the side of the bolt. Consequently, when the round is then fired, the lug 104 will ride the side 136 of the bolt as it recoils and be urged by spring 108 into the boltcatching position 140 as the face of the bolt overrides the location of the lug during the recoil action. As such, the bolt will again be caught by the lug during the counterrecoil action. Thereafter the next round can be fired by simply repeating the operating sequence just described.

While only certain preferred embodiments of this invention have been shown and described by way of illustration, many modifications will occur to those skilled in the art and it is, therefore, desired that it be understood that it is intended herein to cover all such modifications as fall within the true spirit and scope of this invention.

What is claimed as new and what is desired to secure by Letters Patent of the United States is:

l. The combination of a semiautomatic firearm and an assembly modifying the firearm for use as a fully automatic firearm; said semiautomatic firearm comprising a hammer which is spring biased toward a firing position and pivotally movable between a cocked position and said firing position, a sear piece which is mounted for pivotal movement with respect to said hammer and spring biased for movement into latching engagement with said hammer at its cocked position, a trigger piece which is mounted for pivotal movement between a released position and a fully depressed position and arranged to pivotally move said rear piece out of latching engagement with the hammer during movement from its released position to its fully depressed position, and a trigger spring which is arranged to bias said trigger piece into its released position; and said assembly comprising a sear disconnector which is mounted on and movable with said trigger piece and which is maintained on the trigger piece through engagement by said trigger spring, said sear disconnector being arranged to engage said sear piece during pivotal movement of said trigger piece from its released position to its fully depressed position and to maintain said sear piece out of latching engagement with said hammer when the trigger piece is at its fully depressed position.

2. The combination in accord with claim 1 where said sear piece includes a nose portion engageable with the hammer at its cocked position and a tail portion which generally overlies said trigger piece, where said sear disconnector is arranged to engage said tail portion and pivotally move said nose portion out of latching engagement with the hammer as said trigger piece is pivotally moved from its released position to its depressed position.

3. The combination in accord with claim 2 where said trigger piece includes a lip portion and a recessed portion which is located adjacent to said lip portion and which in the absence of said disconnector, receives the tail portion of the sear piece when the trigger piece is fully depressed, where said sear disconnector overlies said lip portion and has a portion that overhangs the recessed portion of the trigger piece to prevent reception of said tail portion in the recessed portion of said trigger piece when said trigger piece is at its fully depressed position.

4. In a firearm having a hammer assembly, a sear assembly, and a trigger assembly arranged in cooperative relation to one another; said hammer assembly including a hammer pivotally mounted on said firearm to move between a first and second position; said sear assembly including a sear piece mounted on said firearm to be movable into engagement with said hammer; said trigger assembly including a trigger piece mounted on said firearm to be movable into contiguous relation to said sear piece, a bolt assembly including a bolt and a firing pin mounted on said bolt in cooperative relation to said hammer; wherein said firearm further comprises a modification assembly including a scar disconnector means carried by said trigger piece and arranged to restrict pivotal movement of said sear piece relative to said hammer, a hammer catch means movably mounted relative to said hammer and arranged to be movable into an interruptive position as said hammer moves from said first position to said second position towards said firing pin; a fire control selector means mounted on said firearm and arranged to be movable into a bolt interruptive position when said bolt is in an open position; thereby maintaining said bolt in an open position; whereby said modification assembly is capable of regulating the firing of said weapon between a semiautomatic and automatic mode.

ill

5. In a firearm as defined in claim 4 wherein said sear disconnector means comprises a one piece element carried entirely on said trigger piece and positioned relative to said sear piece in such a manner as to restrict pivotal movement of said sear piece; thereby preventing engagement of said sear piece and said hammer while said trigger piece is maintained in a depressed position.

6. In a weapon system as defined in claim 4 wherein said hammer catch means comprises: biasing means which movably positions said hammer catch means in the path between said hammer and said firing pin, a lug means positioned relative to said firing pin when said bolt is in a prelocked position such that rotational movement of said bolt during locking of said bolt causes said firing pin to engage said lug means, thereby removing said hammer catch means from an interruptive position as said hammer travels between said first and second position into engagement with said firing pin.

7. The combination of a semiautomatic firearm and an assembly modifying the firearm for use as a fully automatic firearm; said semiautomatic firearm comprising a hammer which is spring biased toward a firing position and pivotally movable between a cocked position and said firing position, a sear piece which is mounted for pivotal movement with respect to said hammer and spring biased for movement into latching engagement with said hammer at its cocked position, a trigger piece which is mounted for pivotal movement between a released position and a fully depressed position and arranged to pivotally move said sear piece out of latching engagement with the hammer during movement from its released position to its fully depressed position, and a recoilable bolt which is rotatable to a locked bolt position at the conclusion of its counterrecoil and which has a firing pin that is rotatable therewith and provided with a lug, said assembly comprising means for maintaining the sear piece out of latching engagement with the hammer when the trigger piece is fully depressed, and a hammer catch device that includes a movable rigid component which has a detent and a lug, and a spring biasing the rigid component into an operating position at which the detent is located in the path of forward movement of the hammer to its firing position to thereby interrupt such forward movement during counterrecoil of the bolt, the lug of said rigid component being located in the path of rotative movement of the firing pin lug when the rigid component is in its operative position, and said rigid component being movable to an inoperative position through engagement of the firing pin lug with the lug of said rigid component as the bolt rotates to its locked bolt position.

8. The combination in accord with claim 7 where said semiautomatic firearm comprises a trigger spring which is arranged to bias said trigger piece into its release position, where said means for maintaining the sear piece out of latching engagement with the hammer when the trigger piece is fully depressed comprises a scar disconnector which is mounted on and movable with said trigger piece and which is maintained on the trigger piece through engagement by said trigger spring, said sear disconnector being arranged to engage said sear piece during pivotal movement of said trigger piece from its release position to its fully depressed position and to maintain said sear piece out of latching engagement with said hammer when the trigger piece is at its fully depressed position.

9. In a firearm adapted for fully automatic usage and having a receiver, a hammer which is spring biased toward a firing position and pivotally movable between said firing position and a cocked position, a trigger piece pivotally movable between a released position and a fully depressed position, a scar piece biased toward retaining engagement with the hammer at its cocked position, means maintaining the sear piece out of such engagement when the trigger piece is fully depressed, and an automatic reciprocating bolt arranged to move between a locked position and a recoiled position, the improvement comprising fire control selector means located exteriorally of the receiver and having a pivotally movable lug, spring means biasing the lug into bolt-retaining engagement with the bolt at its recoiled position, lever means connected to said bolt-engaging lug and finger manipulatable to disengage the lug from the bolt, and means engageable by the lever means to maintain said lug out of engagement with said bolt.

@2 3 UNTTED STATES PATENT @TTTCE QER'HFEQATE @IF @QRREQ'HQN Patent No. 3,626,805 Dated December 14, 1971 Inventor(s) L ewis D. Shipl'ee, III

It is certified that error appears' in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

" Column 1, Line 16, after "there" delete are ma Line 28, before "is" delete it Line 39, delete "for" and substitute of Column 2, Line 61, after "is" delete-s Column 6, Line 54, delete "reason for" and substitute reasons of Line 63, delete "conclusive" and substitute conclusion Column 7, Line 11, delete "into" and substitute to Line 46, delete "the" (third occurrence) and substitute and Column 9,-Line 2, delete "or" and substitute of Column 10, Line 20, delete "rear" and substitute sear Signed and sealed this 13th day of June 1972,

(SEAL) Attes't:

EDWARD MQFLETCHER JR, ROBERT GO'ITSCHALK Attesting Officer Commissioner of Patents zgz gg UNITED STATES PATENT @FFECE CERTFFECATE @F EQEQN Patent No. 2 3,626,805 I Dated December 14, 1971 Inventor(s) .L'ewis D. Shipl'e'e, III

It is certified that erroreppears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

'Tlolumn' 1, Line 16, after "there" delete are 1 Line 28, before "is" delete it Line 39, delete "for" and substitute of Column 2, Line 61, after "is" delete'--'s Column 6, Line 54, delete "reason for" and substitute reasons of Line 63, delete "conclusive" vand substitute conclusion Column 7, Line 11, delete "into" and substitute to Line 46, delete "the" (third occurrence) and substitute and Column 9, -Line 2, delete "or" and substitute of Column 10, Line 20, delete "rear" and substitute sear Signed and sealed this 13th day of June 1972.,

(SEAL) Attest:

EDWARD M.FLETCHER, JR ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

1. The combination of a semiautomatic firearm and an assembly modifying the firearm for use as a fully automatic firearm; said semiautomatic firearm comprising a hammer which is spring biased toward a firing position and pivotally movable between a cocked position and said firing position, a sear piece which is mounted for pivotal movement with respect to said hammer and spring biased for movement into latching engagement with said hammer at its cocked position, a trigger piece which is mounted for pivotal movement between a released position and a fully depressed position and arranged to pivotally move said sear piece out of latching engagement with the hammer during movement from its released position to its fully depressed position, and a trigger spring which is arranged to bias said trigger piece into its released position; and said assembly comprising a sear disconnector which is mounted on and movable with said trigger piece and which is maintained on the trigger piece through engagement by said trigger spring, said sear disconnector being arranged to engage said sear piece during pivotal movement of said trigger piece from its released position to its fully depressed position and to maintain said sear piece out of latching engagement with said hammer when the trigger piece is at its fully depressed position.
 2. The combination in accord with claim 1 where said sear piece includes a nose portion engageable with the hammer at its cocked position and a tail portion which generally overlies said trigger piece, where said sear disconnector is arranged to engage said tail portion and pivotally move said nose portion out of latching engagement with the hammer as said trigger piece is pivotally moved from its released position to its depressed position.
 3. The combination in accord with claim 2 where said trigger piece includes a lip portion and a recessed portion which is located adjacent to said lip portion and which in the absence of said disconnector, receives the tail portion of the sear piece when the trigger piece is fully depressed, where said sear disconnector overlies said lip portion and has a portion that overhangs the recessed portion of the trigger piece to prevent reception of said tail portion in the recessed portion of said trigger piece when said trigger piece is at its fully depressed position.
 4. In a firearm having a hammer assembly, a sear assembly, and a trigger assembly arranged in cooperative relation to one another; said hammer assembly including a hammer pivotally mounted on said firearm to move between a first and a second position; said sear assembly including a sear piece mounted on said firearm to be movable into engagement with said hammer; said trigger assembly including a trigger piece mounted on said firearm to be movable into contiguous relation to said sear piece, a bolt assembly including a bolt and a firing pin mounted on said bolt in cooperative relation to said hammer; wherein said firearm further comprises a modification assembly including a sear disconnector means carried by said trigger piece and arranged to restrict pivotal movement of said sear piece relative to said hammer, a hammer catch means movably mounted relative to said hammer and arranged to be movable into an interruptive position as said hammer moves from said first position to said second position towards said firing pin; a fire control selector means mounted on said firearm and arranged to be movable into a bolt interruptive position when said bolt is in an open position; thereby maintaining said bolt in an open position; whereby said modification assembly is capable of regulating the firing of said weapon between a semiautomatic and automatic mode.
 5. In a firearm as defined in claim 4 wherein said sear disconnector means comprises a one piece element carried entirely on said trigger piece and positioned relative to said sear piece in such a manner as to restrict pivotal movement of said sear piece; thereby preventing engagement of said sear piece and said hammer while said trigger piece is maintained in a depressed position.
 6. In a weapon system as defined in claim 4 wherein said hammer catch means comprises: a biasing means which movably positions said hammer catch means in the path between said hammer and said firing pin, a lug means positioned relative to said firing pin when said bolt is in a prelocked position such that rotational movement of said bolt during locking of said bolt causes said firing pin to engage said lug means, thereby removing said hammer catch means from an interruptive position as said hammer travels between said first and second position into engagement with said firing pin.
 7. The combination of a semiautomatic firearm and an assembly modifying the firearm for use as a fully automatic firearm; said semiautomatic firearm comprising a hammer which is spring biased toward a firing position and pivotally movable between a cocked position and said firing position, a sear piece which is mounted for pivotal movement with respect to said hammer and spring biased for movement into latching engagement with said hammer at its cocked position, a trigger piece which is mounted for pivotal movement between a released position and a fully depressed position and arranged to pivotally move said sear piece out of latching engagement with the hammer during movement from its released position to its fully depressed position, and a recoilable bolt which is rotatable to a locked bolt position at the conclusion of its counterrecoil and which has a firing pin that is rotatable therewith and provided with a lug, said assembly comprising means for maintaining the sear piece out of latching engagement with the hammer when the trigger piece is fully depressed, and a hammer catch device that includes a movable rigid component which has a detent and a lug, and a spring biasing the rigid component into an operating position at which the detent is located in the path of forward movement of the hammer to its firing position to thereby interrupt such forward movement during counterrecoil of the bolt, the lug of said rigid component being located in the path of rotative movement of the firing pin lug when the rigid component is in its operative position, and said rigid component being movable to an inoperative position through engagement of the firing pin lug with the lug of said rigid component as the bolt rotates to its locked bolt position.
 8. The combination in accord with claim 7 where said semiautomatic firearm comprises a trigger spring which is arranged to bias said trigger piece into its release position, where said means for maintaining the sear piece out of latching engagement with the hammer when the trigger piece is fully depressed comprises a sear disconnector which is mounted on and movable with said trigger piece and which is maintained on the trigger piece through engagement by said trigger spring, said sear disconnector being arranged to engage said sear piece during pivotal movement of said trigger piece from its release position to its fully depressed position and to maintain said sear piece out of latching engagement with said hammer when the trigger piece is at its fully depressed position.
 9. In a firearm adapted for fully automatic usage and having a receiver, a hammer which is spring biased toward a firing position and pivotally movable between said firing position and a cocked position, a trigger piece pivotally movable between a released position and a fully depressed position, a sear piece biased toward retaining engagement with the hammer at its cocked position, meaNs maintaining the sear piece out of such engagement when the trigger piece is fully depressed, and an automatic reciprocating bolt arranged to move between a locked position and a recoiled position, the improvement comprising fire control selector means located exteriorally of the receiver and having a pivotally movable lug, spring means biasing the lug into bolt-retaining engagement with the bolt at its recoiled position, lever means connected to said bolt-engaging lug and finger manipulatable to disengage the lug from the bolt, and means engageable by the lever means to maintain said lug out of engagement with said bolt. 